Yes I love Mailbox, the email management app from the folks at Orchestra. I’ve been using it as my default email app for months, and it still serves me well as one of the easiest ways to quickly skim through and archive, delete, reply to, or save emails for later. But over the last few months, I’ve been one of a select few who have had a chance to try it out, as the app was getting ready for a public launch.

If you’re one of those who have been waiting to try it out for yourself, your wait could soon be over, as the app is finally going live in the Apple App Store. Unfortunately, while users will be able to download the app, they might not be able to use it right away. In order to scale up gracefully, Mailbox implemented a reservation system, and will be inviting users on a first-come, first-served basis to begin using it.

Users who have already reserved their place in line will begin receiving notifications when they can download and unlock the app. Those who haven’t done so can download the app from the App Store, which will automatically reserve a spot for them. They’ll also be able to see the line move in real-time, as reservations are opened over time.

Mailbox seeks to make going through email a breeze by allowing users to manage their inboxes with swiping motions. To archive or delete an email, simply swipe to the right. To save for later, swipe left. The save for later feature is particularly helpful in clearing out emails that need responding to, but not immediately, allowing users to delay or “snooze” mail and come back to it.

So why a reservation system? Because Mailbox relies on servers in the cloud to manage push notifications and the all-important “save for later” functionality. As a result, it’s rolling out reservations slowly to ensure that it can provide a quality experience to all users and to keep from getting overloaded while managing demand.

While it’s done a fair amount of load testing in its trial, there’s no replacement for real-world usage to see if something breaks. Since so many people rely on email, the folks working on Mailbox want to ensure that any breakage happening is minimal in the early stages. As a result, they won’t say how quickly they’ll be adding users or how soon those waiting in line can expect to get on board.

For now, the app is for iOS and Gmail (or Google apps), but we’ll probably see integration with other mail systems — and hopefully an Android app — sometime soon. In the meantime, the app makers are looking to just manage iPhone demand. Already, more than 250,000 users have signed up for the iOS launch, according to lead designer Elle Luna.